anv: populate perfetto with last pipe control reason
We can visualize stalls on ANV with Perfetto when using `INTEL_GPU_TRACEPOINT=+stall`. With this change we now display the first four reasons for the flush.
We can visualize stalls on ANV with Perfetto when using `INTEL_GPU_TRACEPOINT=+stall`. With this change we now display the first four reasons for the flush.